The overall objective of this proposed research is to further characterize the functional, hemodynamic, and structural characteristics of unilaterally-diseased kidney models in trained dogs. Studies in Part A are designed to further elucidate the exaggerated natriuresis of diseased kidneys (compared to a contralateral control kidney which maintains a non-azotemic environment) following extra-cellular fluid volume expansion and the diuretic furosemide in a model of unilateral ureteral obstruction presently being developed in our laboratory. The acute and chronic effects of graded unilateral ureteral obstruction will be studied in split-bladder dogs with the use of clearance studies, 133Xe-washout, electromagnetic flow measurements, and silicon rubber injection. Studies in Part B are designed to further elucidate the mechanism of hypertension following unilateral constriction of the renal artery in the presence of a contralateral control kidney in the dog, utilizing an inflatable cuff around the renal artery, a chronic indwelling renal artery catheter, and electromagnetic flow probe. Chronic indwelling renal venous catheters and split-bladders will facilitate measurement of renal blood flow, renin secretion, and urine formation. Studies in Part C are designed to explore in the chicken, using clearance techniques, the 4 component hypothesis which best describes renal urate handling in man and chimpanzee. The renal portal system in the chicken may provide a unique opportunity to selectively study pharmacologic effects on the secretory and post-secretory reabsorptive sites to increase our understanding of renal urate handling in man.